PROJECT SUMMARY Physical activity in early childhood is important for numerous aspects of children's health and development. Preschoolers are thought to be very active but previous studies have shown that they are sedentary for the majority of time and not getting adequate opportunities to engage in active play. Experts have recommended strategies to promote physical activity in early learning settings and to involve parents in efforts to promote active living from a young age. Through early learning settings, we may be able to change behaviors in large groups of children and particularly benefit more vulnerable children who have fewer opportunities for outdoor play and physical activity at home or in their neighborhoods. However, meaningful engagement from families is also important and research suggests that there is gap in communication and perhaps alignment between educators and parents on the topic of preschoolers' physical activity. We propose research that uses wearable technology to monitor physical activity in children, motivate parents and educators to help create active play opportunities, and create a platform for communication and shared accountability about this important health behavior. We will focus particularly on children from lower income backgrounds who suffer from disparities in both health and educational outcomes. In the 2-year R21 phase we propose to evaluate the feasibility, acceptability, and potential efficacy of a 6 month preschool-based, multi-level intervention to promote preschoolers' physical activity using wearable technology and incrementally intensive behavior change techniques to enhance engagement of parents and educators. In the first condition we study, preschoolers and their educators will get wrist-worn activity trackers called Sqord to monitor daily activity levels. In the second condition, we will study whether also giving parents activity trackers and weekly feedback reports about their own and their child's activity help promote more physical activity. Finally, in the third condition, we will add on training and coaching for early childhood educators to align the physical activity intervention with the metrics they are familiar with and evaluated on from an early learning standpoint. We will use the results from the R21 to inform the intervention strategies we include and test more rigorously in the 3-year R33 phase. Our primary outcome of interest is accelerometer measured physical activity. In the R33, we will also explore how changes in preschooler's physical activity relate to cognitive and behavioral indicators of kindergarten readiness, which are topics of great significance to early childhood educators, policy makers and parents.